The Role of Glow Plugs
As time passes, it’s becoming increasingly common to have a sensor for every component in a vehicle. This means that in case of any malfunction or component not working optimally, you’ll immediately be alerted on the dashboard.
Glow plugs are no exception to this rule.
Typically, in an Audi A5, the glow plug warning light or preheating warning light on the dashboard illuminates.
This warning light typically resembles a spiral and is yellow in color.
Here are some key points from the article:
- What Are Glow Plugs?
- The purpose of glow plugs is to heat the air in the combustion chamber.
Another function is to ensure an optimal temperature so that all the fuel in the engine is burned (the extended purpose being to reduce harmful emissions produced during combustion).
Glow plugs also handle this: they provide the necessary heat for the diesel particulate filter (DPF) when it undergoes regeneration. High temperatures, around 600-700 degrees Celsius, are required to transform PM 2.5 and PM 10 particles into soot.
If the engine doesn’t reach the right temperature, the Electronic Control Unit (ECU) activates the glow plugs and injects more fuel into the engine. This process is done to heat the DPF and start regeneration.
Modern glow plugs, with instant heating, also aim to reduce regeneration times, which is essential, especially in urban areas where many drives are short, and regeneration might be interrupted because the engine stops prematurely.
It might not seem obvious, but glow plugs play an important role in Audi A5 by optimizing the engine. If they don’t function optimally, the engine can end up in one of two situations:
If the glow plug doesn’t operate long enough, the engine won’t reach the optimal temperature.
If it operates for too long, the engine temperature will be too high, exceeding normal limits, and over time, the glow plugs or even the engine may become damaged.
When Does the Glow Plug Warning Light Illuminate on Audi A5?
This warning light comes on in the following situations:
When starting the engine (but be aware: if it goes off after a few seconds, everything is fine; this is just a preheating warning).
If one or more glow plugs have burned out.
Issues with the brake pedal switch. You should check if the brake lights are working.
Problems with the pressure and temperature sensor in the intake manifold.
How to Check If Glow Plugs Are Functioning Properly on Audi A5?
As a driver, it’s more challenging to notice potential issues caused by glow plugs, but here are some signs:
The glow plug warning light is illuminated. Be aware that the warning light comes on with every ignition cycle when the engine is cold. If it goes off after a few seconds, everything is fine; it’s just a preheating warning. However, if the warning light remains on for more than 20 seconds, there might be a problem.
The car emits either white or black smoke from the exhaust.
White smoke appears when there isn’t enough heat to burn the fuel completely, resulting in incomplete combustion. In this case, white smoke and a strong odor are emitted from the exhaust.
Black smoke indicates an imbalance in the air-fuel ratio, with too much fuel and too little air.
In the situations mentioned above, it is recommended to take the car to a service center.
Mechanics have various tools to check for glow plug problems, including:
Physically inspecting the glow plugs, which are removed from the engine. Once inspected, an experienced eye can determine whether they are still good or on the verge of failure. This process includes measuring the ohmic resistance of each glow plug, and the glow plug is functional if the resistance value doesn’t exceed 0.5 ohms.
It is recommended that when the glow plugs are removed, either for inspection or replacement, the housing where they are located should be cleaned of any dirt.
Glow Plug Maintenance:
Please note: using high-quality fuel in the Audi A5 (preferably premium) will ensure a longer life for the engine’s glow plugs.
It’s advisable to use glow plugs recommended by the manufacturer.
Regularly check the glow plugs, preferably during scheduled maintenance, as well as the system that ensures the functioning of the glow plugs. This step is more complex and involves checking several components such as glow plugs, the control module, relay systems, fuel pumps, and injectors, the Engine Management System (EMS), and the battery. Therefore, the intervals in terms of time or kilometers may be longer for this process.
Once the ignition is turned on, the driver should wait for the glow plug warning light to go out. If the engine is warm, this happens almost instantly. However, if the engine is cold during the initial ignition, it’s normal for the warning light to stay on for several seconds. Nevertheless, any interval longer than 20 seconds indicates a problem with the car.
Cost of Replacing Glow Plugs on Audi A5:
The cost depends on several factors:
- The car’s year of manufacture.
- Whether you buy original or aftermarket glow plugs (but recommended by the manufacturer).
- The cost of service. Although indirect, this cost will arise. Removing the glow plugs is a simple process but requires a special tool that not everyone has.
However, it’s worth noting that the price of glow plugs is relatively low, starting at around 5 euro per plug. Since it’s recommended to replace all four at once, you’ll likely spend at least 30 euro for the parts. It’s ideal to purchase high-quality glow plugs, even if they cost a bit more. These components are worth the investment as they don’t deteriorate frequently and play a crucial role in the optimal functioning of the engine. Labor costs will also be added to this cost.